gmp_random

说明

Generate a random number. The number will be between
zero and the number of bits per limb multiplied by
limiter. If limiter
is negative, negative numbers are generated.

A limb is an internal GMP mechanism. The number of bits in a limb is
not static, and can vary from system to system. Generally, the number
of bits in a limb is either 16 or 32, but this is not guaranteed.